Diseases of the heart are a leading cause of death in the developed world. One exemplary disease of the heart is heart failure, afflicting over 5 million people in the United States, according to The National Heart Lung and Blood Institute (NHLBI). Heart failure refers to a clinical syndrome in which an abnormality of cardiac function causes a below normal cardiac output that can fall below a level adequate to meet the metabolic demand of peripheral tissues.
Ischemia is a condition that can be associated with many types of heart disease. Ischemia can be described as an inadequate flow of blood to a part of the body, caused by constriction or blockage of the blood vessels supplying it. Ischemia can be a very serious condition depending on what part of the body is receiving an inadequate flow of blood. For example, ischemia can result in myocardial infarction where parts of the myocardium fail to receive an adequate flow of blood because of a blockage or constriction in the coronary artery.
Monitoring patients' physiological state is an important aspect in the diagnosis, management and treatment of diseases and conditions of the heart, including heart failure and myocardial ischemia. As such, various monitoring systems have been developed over time. Many of these monitoring systems rely on sensing electrical activity of the heart and then evaluating this activity in order to determine the patient's physiological state. However, a need remains for additional types of monitoring systems that can provide accurate information about a patient's physiological state.